A leading Christian campaigner for same-sex relationships in Northern Ireland has welcomed the Bishop of Grantham's announcement that he is in a gay relationship.

The Church of England's Rt Rev Nicholas Chamberlain caused controversy last week after revealing he is in a long-term, celibate relationship with his male partner. His announcement was a bid to pre-empt a Sunday newspaper intending to out him.

Richard O'Leary, a member of St George's congregation in Belfast, is a co-founder of Changing Attitudes, a pro-gay lobby within the Church of Ireland. He was in a long-term relationship with Rev Mervyn Kingston, a former rector in the border parish of Creggan and Ballymascanlon, who died three years ago.

Mr O'Leary said he hoped the Bishop's initiative would lead to greater awareness of the subject, and help gay clergy and laity.

Commenting on Bishop Chamberlain's announcement that he was committed to celibacy in order to comply with the rules of the Church of England, Mr O'Leary said: "It is cruel to expect a person in a long-term relationship to make a commitment to celibacy, whatever that means.

"Does it mean sharing a bed, or holding hands?

"This is a preposterous situation, and it is a form of intrusion into intimate and private relationships. If people are in a long-term and loving relationship, I don't think it is appropriate for others to make such enquiries into these situations."

However, Rev Trevor Johnston, rector of All Saints' parish in Belfast said Bishop Chamberlain's admission had caused "deep concern among orthodox Anglicans".

He said it was unfortunate that the Bishop "has given in to our current socio-political climate, where the maelstrom around sexuality and gender, reduces human beings to their sexual preferences".

"Unfortunately, while adhering legalistically to the 'letter of canon law', obedience to the word of God through living wisely (and avoiding all possible reproaches and temptations) appears not to have been high on the agenda."

He said many people looking in on this situation "will be confused, concerned and disillusioned" and more pressure would be put on the Church to revise its teaching.

A Church of Ireland spokesman said: "We would not typically comment on matters relating directly to the Church of England.

"In accordance with its General Synod resolution of 2012, the Church of Ireland seeks to welcome and make disciples of all people, while upholding the teaching that marriage is between a man and a woman."